Green Roofs

Discussion in 'HVAC Heating & Cooling' started by gormanwvzb, Jun 28, 2008.

  1. gormanwvzb

    gormanwvzb New Member

    Messages:
    1
    Terry,

    I have been reading a lot about re-doing my house and I have gotten interested in green roofs. They offer a lot in terms of energy efficiency and help reduce air pollution.

    What do you know about them?

    I have been reading a lot about them on a blog called Clean Air Through Green Roofs found at http://www.cleanerairfocities.blogspot.com

    Thanks!

    [​IMG]
    Last edited by a moderator: Jun 28, 2008
  2. Terry

    Terry Administrator Staff Member

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    15,412
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    Bothell, Washington
    Not much, that's what my roof looks like though,
    Guess I better either water it, or sweep it.
  3. jadnashua

    jadnashua Retired Defense Industry Engineer xxx

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    22,313
    Location:
    New England
    Building a house into the side of a hill and backfilling around the sides and roof can be hugely efficient, but needs careful attention to details to not feel claustrophobic (skylights help alot). Waterproofing must be done very carefully, too or you'll have lots of trouble, whether it was in the side of a hill, or with just a garden or sod on top.

    There's at least one company that makes roofing panels made to interlock and are built out of photocells. Another company makes rubber roofing shingles made of recycled tires that look like slate.
  4. Bob in Maine

    Bob in Maine New Member

    Messages:
    14
    Green roof

    If you have a low-sloped roof, you might take a look at one of the modular green roof systems like GreenGrid.

    http://www.greengridroofs.com/

    They basically assemble 2x4 ft shallow planters that can be fastened together to cover a large roof area. The planting material contains very few fines, so it doesn't wash away, and the company will specify plants that are appropriate for your climate.

    This is much easier than trying to come up with a roof system that can hold soil and plants without leaking.

    To save money, I think they'll sell you the bits and pieces to assemble the panels yourself, or I suppose you and your local garden store could come up with your own version of this.

    In any case, you'd have to make sure your roof framing was adequate to carry the extra dead load, including the extra water the panels would hold.

    I'm not sure how you could accomplish something like this with your basic sloped residential roof.
  5. Bob NH

    Bob NH In the Trades

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    3,317
    Location:
    New Hampshire
    You could put quite a garden on the roof within the weight limits of most roof systems.

    Most roof systems are designed for snow loads of 20 to 50 pounds per square foot depending on location.

    You could start with a ^ straddling the ridge line. The ^ must be constructed so it is rigid like a truss. The part straddling the ridge prevents the stringers/supports from sliding down the roof.

    If you want to make water-tight penetrations at the ridge line you can fasten the stringers at that point to keep them from sliding down the roof. I think I would do that rather than the rigid/reinforced ^ structure. I would put one water-tight attachment point at the ridge, at each truss/rafter, to attach sleepers going down the slope of the roof.

    The supports would be lined up over the rafters or trusses and just the weight of the garden would hold it in place. Put some extra weight at the ends over the outside walls to prevent uplift.

    Now add some horizontal pieces like planters across the stringers. It could be something to set pots on.

    You probably want some kind of watering system because there will not be a lot of soil to hold water from rainfall.

    Leave room for steps to service the garden, unless you can easily walk on the roof.

    The idea is to lay out the supports for planters or other garden features without penetrating the weather shield of the roof. All of the parts contacting the roof should be down the fall-line so there are no dams to prevent runoff.

    I would make it modular so it would be easy to disassemble and remove if it is necessary to service the roof. If you are in a heavy snow area you may want to remove it for the winter.
  6. jadnashua

    jadnashua Retired Defense Industry Engineer xxx

    Messages:
    22,313
    Location:
    New England
    The combined weight of the planters, soil, plants, and any water they can hold PLUS a winter snow load would overcome most roofs. If you aren't in a snow area, the roof may not be built for snow loads, which means even less margin. You need to probably start with a new building for something like this or carefully evaluate your existing situation otherwise, the roof might just end up in your bedroom, hopefully not with you in the bed.

    Surface things like recycled materials or photovoltaics, or solar collectors are more practical green retrofits to an existing roof IMHO. Leave the roof gardens for a new building, built to accommodate it.
  7. JEFutch

    JEFutch New Member

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    1
    Other than planting flowers, vegetables and minimalist shrubbery on your rooftop, what can the urban homeowner or stand-alone business building do to achieve a green roof?
    The least complex method would be to choose roofing surfaces that are accredited by the Cool Roof Rating Council and Energy Star, a federal program that has saved Americans about $12 billion dollars on utility bills since 2005. Energy Star rates roofs, major appliances, home electronics, and lighting. Since Energy Star first began examining how to reduce bills and energy used in 1998, by assessing how to lower the amount of heat absorbed through a roof, it has discovered that one-sixth of all consumed energy is a result of air conditioning, amounting to roughly $40 billion a year.
    The key feature to saving energy is reflectivity. If heat is deflected away from the building and not absorbed, energy costs immediately decrease. For the custom homeowner, finding out which materials can stimulate reflectivity is invaluable. J.E.Futch Custom Homes Inc. is adept at assisting in selecting the best materials and roof colors that promote a healthy environment. For instance, the lighter the tile, the more enduring and heat resistant. As an example, white tile reduces heat gain in your attic, and easily outshine shingle roofs for reflectivity. Using waterproof coatings from naural products or coating masonry with polymers that have zero permeability, will render them 100 percent waterproofed.
    An Energy Star roof reduces the amount of heat absorbed by deflecting the rays away form a building. Think hot Florida days… temperatures holding steady in the mid-to high 90s. Then think about an Energy Star roof that can reduce that heat pounding on your roof by as much as 100 degrees. If your roof is less hot, the drain on your air conditioning will be less, possibly saving as much as 10-15 percent during peak daytime periods. Florida homes use R-Value insulation in an attic, but the smart homeowner uses as high an R-Value as possible, eliminating the occurrence of heat loss.
    Of course, if you live in the inner city, or are simply looking to set an example of what a real green roof is about, you could plant vegetation and soil over a waterproofed membrane on top of your roofing materials. A root barrier, drainage, and irrigation systems must be considered within your design. Popular in Europe, roof gardens are becoming the trend for celebrities, environmentalists, and advance-thinkers in the United States.
    The more cities pave over green areas, destroy trees and natural habitats, the more necessary to recreate that loss in our individual spaces. Green roofs are like sponges, absorbing water that would otherwise run off. Research shows that three-to-five inches of soil or other growing medium can absorb about 75% of rain (one-half inch or less) and they filter out pollution from the rain.
    While having a genuine green roof might encourage your green thumb, filter out pollutants, and make you feel like you are saving the environment one day at a time, keep in mind that at this time, properly creating and maintaining that roof is currently more costly than using green roofing materials that your custom homebuilder can suggest.
  8. Southern Man

    Southern Man DIY Hillbilly

    Messages:
    530
    Location:
    North Carolina
    The only practical way to make an existing roof "green" is to insulate it as much as possible then install surface mounted solar panels.
  9. hj

    hj Moderator & Master Plumber Staff Member

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    27,235
    Location:
    Cave Creek, Arizona
    green

    Mother Nature is a very persistant person. The roots from that green roof will attack whatever they are planted on. One company tried to make earth insulated houses by using very large highway culverts with earth mounded over them. It was not too many years before they had a ceiling full of roots hanging down.
  10. Southern Man

    Southern Man DIY Hillbilly

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    530
    Location:
    North Carolina
    An indoor garden!
  11. nhmaster

    nhmaster Master Plumber

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    3,189
    Location:
    S. Maine
    Until this thread I thought I had seen just about every hair brained nut case, moon bat green scheme possible but truley this lunacy takes the prize. Holey hopping horney toads Bat Man, the whole world's gone nutz.
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